Tuna Meatballs with Tomato Sauce - Polpette di tonno con salsa di pomodoro

Meatballs

• 50 g Parmesan cheese, cut in pieces (2 cm)
• 100 g white bread, torn in pieces
• 10 g fresh parsley leaves, plus extra for garnishing
• 400 g fresh tuna, cut in pieces (3-4 cm)
• 55 g toasted pine nuts
• ½ tsp ground cinnamon
• 1 tsp dried oregano
• 2 medium eggs
• 1 lemon, finely grated zest and juice

Sauce

• 20 g olive oil, plus extra for frying
• 60 g onions, halved
• 2 garlic cloves
• 800 g tinned peeled plum tomatoes (2 x 400 g tins)
• 1 tsp dried oregano
• 1 tsp sugar (optional)
• fine sea salt, to taste
• ground black pepper, to taste
• red wine vinegar, to taste (optional)